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Physicists calculate when the last supernova will ever occur



Physicists calculate when the last supernova will ever occur

An artist̵

7;s concept of a dark brown dwarf, which may resemble the black dwarfs predicted to form in the future. Credit: NASA / JPL-Caltech

The end of the universe as we know it will not come with a bang. Most stars will slowly fade as their temperatures fade to zero.

“It will be a sad, lonely, cold place,” said theoretical physicist Matt Caplan, who added that no one will be around to witness this long farewell happening in the distant future. Most believe that everyone will be dark as the universe ends. “It’s known as ‘death of heat,’ where the universe will be mostly black holes and burning stars,” said Caplan, who imagined a slightly different view when calculating how some of these dead stars could vary during eon.

The embellishment of darkness could be silent fireworks – explosions of star debris that should never have exploded. New theoretical work by Caplan, an assistant professor of physics at Illinois State University, reveals that many white dwarfs could erupt into supernovae in the distant future, long after everything else in the universe is dead and gone.

In the universe now, the dramatic death of massive stars in supernova explosions comes when internal nuclear reactions produce essentially iron. Iron cannot be burned by stars – it accumulates like a poison, causing the star to collapse creating a supernova. But smaller stars tend to die with a little more dignity, shrinking and becoming white dwarfs at the end of their lives.

“Stars less than about 10 times the mass of the sun do not have the gravity or density to produce iron in their nuclei as massive stars do, so they cannot explode into a supernova right now,” Caplan said. “As white dwarfs cool down over the next few trillion years, they will fade, eventually freeze solid, and become ‘black dwarf’ stars that no longer shine. “Like white dwarfs today, they will be made mostly of light elements like carbon and oxygen and will be the size of the earth, but contain about as much mass as the sun, their insects squeezing in densities millions of times greater than any thing on earth.

But just because they are cold does not mean that nuclear reactions stop. “Stars glow because of the hot thermonuclear fusion they are hot enough to hit small nuclei together to make larger nuclei, which releases energy. White dwarfs are ash, they are burned out, but fusion reactions can still happen because of the quantum tunnel, only Much slower, Caplan said. “Fusion happens, even at zero temperature, it only takes a really long time.” He noted that this is the key to turning black dwarfs in iron and the induction of a supernova.

Caplan ‘s new work, accepted for publication by Monthly Announcements of the Royal Astronomical Society, calculates how long it takes these nuclear reactions to produce iron, and how many black iron dwarfs of different sizes must explode. He calls his theoretical eruptions “black dwarf supernovae” and estimates that the first will occur in about 10 to 1100. “For years, it’s like saying the word ‘trillion’ almost a hundred times. If you wrote it “It will take up most of a page. It ‘s very far in the future.”

Of course, not all black dwarfs will explode. “Only the largest black dwarfs, about 1.2 to 1.4 times the mass of the sun, will blow.” However, this means that 1 percent of all stars that exist today, about one billion trillion stars, can expect to die this way. As for the rest, they will remain black dwarfs. “Even with very slow nuclear reactions, our sun still does not have enough mass to ever explode in a supernova, even in the distant future. You can turn all the sun into iron and it still would not fall.”

Caplan calculates that the largest black dwarfs will explode first, followed by gradually less massive stars, until there are no more left to disappear after about 1032000 years. At that point, the universe can really be dead and silent. “It’s hard to imagine anything coming after that. The black dwarf supernova could be the last interesting thing that happens in the universe. It could be the last supernova ever.” By the time the first black dwarfs explode, the universe will already be unknown. “Galaxies will be scattered, the black hole will have evaporated, and the expansion of the universe will have pulled all the objects left so far away so that no one will ever see any of the others explode. nor is it physically possible for light to travel so far ”

Although he will never see one, Caplan remains useless. “I became physical for a reason. I wanted to think about the big questions – why is the universe here and how will it end?” When asked what the big question is next, Caplan says, “Maybe we’ll try to simulate some black dwarf supernovae. If we can not see them in the sky, we can at least see them in a computer. ”


The ghosts of ancient explosions live in the stars today


Provided by Illinois State University



citation: Physicists calculate when the last ever supernova will occur (2020, August 13) Retrieved August 13, 2020 from https://phys.org/news/2020-08-physicists-supernova.html

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